synadelphus

syn·a·del·phus

(sin'ă-del'fŭs),
Conjoined twins with single head, partially united trunk, and four upper and four lower limbs. See: conjoined twins.
[syn- + G. adelphos, brother]

synadelphus

(sĭn″ă-dĕl′fŭs) [″ + adelphos, brother]
A deformed fetus with eight limbs.